Electrical machines which feature a stator and a rotor are already known. The rotor features a rotor shaft which is supported in rotor bearings. These types of electrical machine are employed in areas such as drives for auxiliary equipment in motor vehicles and can be used there as window lifting motors or as pump drives for example. The practical problem which arises with such machines is that radial and axial play occurs between the stator and the rotor. This leads to undesired noise during operation and furthermore also to a reduced lifetime of the rotor bearing.
An arrangement for setting of the axial play between the rotor and the stator of an electric motor is already known from DE 35 34 381 C2. With this known arrangement a bearing which is fixed under normal operating conditions is embodied for the rotor shaft as a cylinder bearing. To set the axial play the cylinder bearing can be shifted axially relative to its stator-side bearing end plate holder by a pressure greater than the axial load arising during normal operation.
A bearing arrangement for rotors of electrical machines is known from DE 42 06 761 C2 which contains two ball races to accept the ends of the rotor shaft. The inner rings of the two ball races are each mounted onto the bearing surfaces of the rotor shaft by means of an interference fit so as to prevent movement along the shaft. The associated outer rings of the ball races are supported in bearing end plates of the motor housing in a sliding fit. Furthermore the known arrangement features an axial adjusting spring supported on a bearing end plate which acts on the outer ring of one of the ball races. The two bearing end plates consist of metal parts or aluminum parts and feature cylindrically embodied, deep-drawn bearings. They are held together by means of spacer profiles under tensile stress. The adjusting spring is implemented as a wave spring which rests against the base of a deep-drawn bearing end plate and transfers its pressure force via the outer ring of the first ball race onto its inner ring, from there via the rotor shaft to the inner ring of the second ball race and then to its outer ring. This creates a ball race arrangement in which a long lifetime is obtained at low cost and with little noise generated even with high axial bearing loads.